Waves and oscillations in sunspot atmosphere: a review

The review focuses on recent experimental and theoretical studies of sources of oscillations in the sunspot atmosphere. The results of observations with ground-based and spaceborne instruments are presented. An important role of the cut-off frequency in forming the spatial distribution of narrowband sources of oscillations above sunspot is shown. The alternative techniques for studying the magnetic field structure by using helioseismological data are discussed. The dynamics of propagating wave fronts is studied by applying the pixelized wavelet filtering technique. The height analysis of oscillation parameters is performed. A possibility to initiate flare energy release by MHD waves propagating along magnetic waveguides from sunspots into the flare region is discussed. The attention is paid to processes of the increase in wave activity in sunspots before the flare energy release. A brief description of the theoretical model for oscillations based on the subphotospheric low-frequency resonator is provided.